APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY-
SECOND SEMESTER M.TECH DEGREE EXAMINATION, APRIL-MAY 2017
Electrical & Electronics Engineering
(Electrical Machines, Power Control & Drives)
OIEE6302 Electric Drives
Max. Mark: 60 Duration: 3 Hours

Answer _(wa lull quesgions (rom each Par(

PART-I

1.4) A weight of 500kg is being lifted up by a uniform speed of 1.5m/s by a winch driven by a motor running at
a speed of 1000rpm.The moment of inertia of the motor and the winch are 0.5 and 0.3 kgm respectively. 2
Calculate the motor torque and equivalent moment of inertia referred to motor shaft. In the absence of weight,
motor develop a torque of ‏ص100‎ when running at | 000൬൩.

(S mark)

b) Draw the block diagram of electric drive system and explain the important functions of Power modulator. (At
least four numbers).

(4 mark)

2. a) Derive the open loop transfer function of separately excited DC motor for speed control and obtain the step
response due to change in load.

(5 mark)

b) Derive the average value of output voltage of single phase full converter for continuous and discontinuous
modes of operation.

(4 mark)

3. a) What is regenerative braking? Describe the regenerative braking of chopper fed separately excited DC
motor. Illustrate your answer with circuit diagram and wave forms.

(7 mark)

b)Derive the expression for minimum and maximum braking speed for obtaining regenerative
braking of DC motor.
(2mark)
PART-2

4. (a) Explain the stator voltage control method of speed control of induction motor using suitable equations and
characteristics. Using semiconductor voltage controller, explain how the stator voltage can be controlled to
operate the motor in two quadrants.

(10 mark)